1. Field of Invention
The invention relates to a joint for structural members, such as floor panels.
2. Description of Related Art
A joint floor for floor panels is for instance disclosed in EP 0 698 162 B1. In the case of this known, so-called xe2x80x9cglue-freexe2x80x9d joint, the adjacent circumferential edges of the panels are joined by a groove and tongue joint. There, the lower groove cheek of the one panel facing the contact face is extended beyond the vertical parting plane and comprises a locking projection at its end portion, the locking projection immersing in a corresponding recess of the tongue of the other floor panel. In order to facilitate the laying of the panels, the joint in the engaging portion of the extended groove cheek with the tongue is performed with play so that displacing of the panel along the longitudinal edges is rendered possible.
WO097/47834 A1 shows a generic joint in which, similar to the solution described above, the lower groove cheek of a floor panel is extended beyond the vertical parting plane and is provided with a projection which engages with a corresponding clamping recess of the tongue. Contrary to the solution initially described, the engagement between the extended groove cheek and the corresponding recess of the tongue is performed such that a force is exerted by this locking which presses the two floor panels towards each other perpendicular to the vertical plane.
In both solutions described above, the groove and tongue joint has a double function. The groove and tongue joint on the one hand ensures the accurately fitting positioning of the two floor panels relative to each other so that no gaps and projections occur and the required laying quality is guaranteed. The second function consists in ensuring this predetermined relative position by the non-positive or positive locking between the extended groove cheek and the tongue even in the case of strain on the floor or temperature and moisture fluctuations.
It is a problem with the known solutions that the extended groove cheek has to be resiliently deformed to perform the engagement between the locking elements. In the case of unfavourable conditions, for instance with excessive strain of the resilient lower groove cheek or in the case of swelling due to moisture and the influence of temperature, cracks may occur in the contact area of lower grove cheek with the pertinent floor panel so that the groove cheek can no longer fulfil the locking function described before. In addition, the quality of the fitting of the groove and tongue joint is aggravated in the case of such cracks occurring in the contact area, so that the accuracy required for correct floor laying is no longer guaranteed.
As compared to this, it is an object of the present invention to provide a joint for structural members, in particular floor panels, in which an accurately fitting relative position is ensured with a minimum of equipment required.
Pursuant to the invention, fitting and locking are assumed by two separate structural members. Fitting is performed conventionally via a groove and tongue joint while locking is performed via a twistlock formed at a distance to the groove and tongue joint and thus being functionally independent thereof. The twistlock may be formed at the tongue-side front face or at the groove-side front face of a floor panel.
In preferred embodiments, the twistlock is formed at a distance to the tongue and immerses in a recess at the lower, floor-side groove cheek which, contrary to the prior art, is not resilient. This means that both the tongue and the twistlock are passing the vertical parting plane between the structural members in horizontal direction and are each immersing in corresponding recesses of the opposite structural member. With these embodiments, it is of particular advantage that substantially less material has to be removed relative to the solutions initially described, so that the shaping process for processing the front faces is facilitated.
A particularly reliable locking, which is easy to be manufactured, is obtained when the twistlock is provided with a recess with which a projection at the bottom of the lower groove cheek engages. The contact area between groove cheek and twistlock is preferably designed as inclined face, so that, even with relatively great tolerances, the applying of a predetermined prestress force admitting the two structural members to move towards each other is ensured.
The twistlock advantageously extends along the lower side of the structural member, so that a high-quality visible and stepping surface can be produced.
It is of very particular advantage if a groove is formed between the twistlock and the tongue, the depth of which determines the resilience of the twistlock relative to the vertical parting plane. This means that the tension forces applied by the twistlock and the extraction forces for taking apart the structural members can easily be adapted to varying ambient conditions or materials by changing the depth of this groove.
The invention may for instance be used with laminate floors having a carrier plate of high-pressure or medium-pressure wood fibers. On principle, the glue-free joint pursuant to the invention may also be used with other floors, for instance parquet floors.
Another advantage of the joint pursuant to the invention consists in that the structural members can be joined and locked with each other by sliding along the floor face. In the case of the prior art initially mentioned it is, however, necessary to first of all incline one structural member relative to the other structural member so as to insert the tongue in the groove, and to subsequently cause locking by twisting to the plane position. This means that, by providing floor panels with the locking pursuant to the various exemplary embodiments of the invention, the laying of the floor can be performed in a substantially easier and quicker way.
The sliding faces along which the structural members are sliding during the locking process are preferably designed as inclined faces.
When the structural members are laid flatly side by side, preferably both the longitudinal edges and the side edges of the structural members are joined pursuant to the invention.
In addition to the locking described before, the structural members may also be glued.
In one exemplary embodiment of the invention, the tongue and the twistlock may be made so that the front face of one of the tongue and the twistlock extends further beyond the vertical parting plane than the front face of the other of the tongue and the twistlock. In another exemplary embodiment of the invention, the tongue and the twistlock may be made so that the front faces of the tongue and the twistlock extend substantially the same distance beyond the vertical parting plane.
Advantageous further developments of the invention are set forth in the various exemplary embodiments described herein.